We learn this from looking at which authors are the most popular and which stories are most commonly chosen for ridicule, either through flaming or through “MSTing.”

2011, Michael Dean, "Frame work, resistance and co-optation: How Mystery Science Theater 3000 positions us both in and against hegemonic culture", In the Peanut Gallery with Mystery Science Theater 3000: Essays on Film, Fandom, Technology, and the Culture of Riffing, ISBN0786445327, page 126:

Most MSTers confine their "riffing" to original fan fiction rather than scripts from corporate-owned entertainment properties, which renders such twice-removed MSTing somewhat toothless: the cannibalizing parody of a patische.

2011, Ron Hale-Evans, Marty Hale-Evans, Mindhacker: 60 Tips, Tricks, and Games to Take Your Mind to the Next Level, ISBN1118166434: